*** NOTE: You can avoid having to make any ugly hacks to your PC by simply
upgrading to XP SP3 final. Get the download of the SP3 ISO from the
home page.

So after much dismay regarding Microsoft's "lack" of support for WebApp on
the xP OS, I set out on a quest to obtain as much information as possible on
this solutions. After hearing about some people's success in getting the RDP
bits from XP SP3 RC2 to work, I upgraded my PC to this release and it STILL DID
NOT WORK!

Finally I located a
RAR file from
http://www.terminalserviceslog.com/ with the mystery files enclosed - these
seemed to do the trick ONLY ONCE I copied the entire contents to the
C:\Windows\System32 folder then ran regsvr32
c:\windows\system32\mstscax.dll (this is the NEW Terminal Services
ActiveX control for web-based access) from the command prompt.

Since I have many dreams of using WebApp for my medical clients (since their
current Citrix hosting provider is 18 month out with no resolution to the
slowness for their hosted application), I needed a way to quickly deploy RDP 6.1
support in an xP environment.

Here is my process:

Install RDP 6.0 from
Microsoft. If you have everything closed you can typically avoid a
reboot :)

Update the RDP install to 6.1

I've created a nifty ZIP package that will take the guesswork out of the
process.
Download here

Upon running update.bat (included in the download above)
this package:

Copies the necessary RDP 6.1 support files to the C:\Windows\System
folder.

Copies mstsc.exe and mstscax.dll to the necessary Windows folders to
prevent the original files from mysteriously creeping back onto your system.
You can take Windows File Protection for this.

Registers the mstscax.dll - THIS IS KEY TO THE WHOLE PROCESS!

Once I launched into my WebApp portal, I had to allow the ActiveX control to
run (or alternately, add the URL to my Trusted Sites). This did the trick, and I
was able to load up the WebApp portal plus connect to any of the "published"
applications on any xP platform.

Special thanks to Richard Gard for the recommended changes to avoid
Windows File Protection reverting these changes.